Every action of a non-amenable group is the factor of a small action
Dynamical Systems
2014-07-07 v2 Group Theory
Logic
Abstract
It is well known that if is a countable amenable group and factors onto , then the entropy of the first action must be greater than or equal to the entropy of the second action. In particular, if has infinite entropy, then the action does not admit any finite generating partition. On the other hand, we prove that if is a countable non-amenable group then there exists a finite integer with the following property: for every probability-measure-preserving action there is a -invariant probability measure on such that factors onto . For many non-amenable groups, can be chosen to be or smaller. We also obtain a similar result with respect to continuous actions on compact spaces and continuous factor maps.
Keywords
Cite
@article{arxiv.1311.0738,
title = {Every action of a non-amenable group is the factor of a small action},
author = {Brandon Seward},
journal= {arXiv preprint arXiv:1311.0738},
year = {2014}
}